1. Field of the Invention
This invention relates generally to an ink pump control system, and more specifically to an ink pump control system for optimally controlling ink feed by controlling the revolution of a stepping motor as the drive unit of the ink pump in accordance with printing speed and printing element ratio (the ratio of printing element area to the sum of a printing element area and a non-printing area on a plate surface to which ink is to be fed).
2. Description of the Prior Art
There are various types of ink feeders for feeding ink to printing presses for printing newspaper and other printed matter. Among such ink feeders, a construction of an ink feeder in which an ink pump installed on a printing press is driven by a stepping motor, and ink feed is changed by controlling the revolution of the stepping motor in accordance with each input data of printing speed, printing element ratio and printing density is publicly known. (Refer to Japanese Published Unexamined Patent Publication No. Hei-1(1989)-174446 and Japanese Published Unexamined Patent Publication No. Hei-1(1989)-174447, for example.)
In the aforementioned publicly known ink pump control system, a frequency division ratio for dividing a basic clock frequency (oscillation frequency) is obtained based on each input data of printing speed, printing element ratio and printing density, and frequency division pulses obtained by dividing the basic clock frequency at the frequency division ratio obtained are applied to the stepping motor as the drive unit of the ink pump to effect control so that the optimum ink feed at a given moment can be obtained in accordance with the printing state at that moment.
With the conventional construction, however, calculation based on printing speed and printing density, calculation based on printing element ratio, and frequency division of the basic clock by means of an oscillating circuit based on these calculations are carried out by a CPU. This requires an ink pump control system to have a CPU capable of highly complex calculation and processing, resulting in increased manufacturing cost of the system.
Furthermore, the control accuracy of the ink pump control system tends to be lowered due to accumulated errors involved with numerous calculations, signal output processing based on the calculations, frequency division based on the outputted signals.